1. Field of the Invention
The invention relates to a device for rolling of pipe blanks, having a planetary cross-rolling mill, having a pipe blank advancing unit that pushes the pipe blanks through the planetary cross-rolling mill, proceeding from the advancing bed, which unit has at least one advancing apparatus, having a mandrel rod and having a mandrel rod holder. The pipe blank feed has an axial pipe blank conveying unit that conveys a pipe blank axially into a readiness position, which is provided axially behind the mandrel rod holder. The advancing apparatus is disposed between the planetary cross-rolling mill and mandrel rod holder.
The invention also relates to a method for rolling pipe blanks in a planetary cross-rolling mill, in which the pipe blanks are conveyed to the planetary cross-rolling mill continuously, end to end, and two alternating advancing apparatuses push the pipe blanks into the planetary cross-rolling mill.
Furthermore, the invention relates to a method for rolling of pipe blanks in a planetary cross-rolling mill, in which the pipe blanks are conveyed to the planetary cross-rolling mill separate from one another.
2. The Prior Art
Devices and methods for pipe blank rolling are known from the state of the art concerning the production of pipes, in many different ways. For example, a method for rolling of pipe blanks in a planetary cross-rolling mill and a device for conveying pipe blanks into the planetary cross-rolling mill, with which the performance of a planetary cross-rolling mill can be increased, are described in German patent DE 101 26 411 B4.
For this purpose, it is proposed, in German patent DE 101 26 411 B4, that the feed of the pipe blanks to be rolled into the roll nip takes place continuously, end to end, and the pipe blank that follows the pipe blank situated in the roll nip, in each instance, is pushed forward with a rotation that corresponds to the rotation of the pipe loop end brought about by the torsion under the rolls. To implement this method, a device for conveying pipe blanks into the planetary cross-rolling mill is provided. In the planetary cross-rolling mill, each pipe blank can be rolled out by way of an interior tool that is held fixed in place in the roll nip. The device comprises a first and a second holding apparatus for the mandrel rod, disposed at an axial distance from the former, which holding apparatuses can be set radially against the mandrel rod independent of one another, as well as a first and a second advancing apparatus for the pipe blank, which can be set radially against the pipe blanks, independent of one another, and can be displaced with the latter, in the advancing direction and/or counter to it. Furthermore, a device for pushing a new pipe blank onto the rear end of the mandrel rod that is held in the rolling position, during rolling of a previous pipe blank, is provided. The movement of the holding apparatuses and that of the advancing apparatuses are coordinated with one another in such a manner that the rear end of the previous pipe blank and the front end of the subsequent pipe blank can be conveyed to the roll nip end to end, and the advancing direction has a clamping chuck mounted so as to rotate freely about the longitudinal pipe blank axis.
The restricted available stroke of the pipe blank advancing apparatuses, which are generally configured as advancing carriages that can move back and forth, is a disadvantage of the planetary cross-rolling mills that operate continuously, of the type stated. Because of the restricted stroke of the advancing carriages, a frequent change of the advancing carriages that are in engagement with each pipe blank takes place. This frequent change of the advancing carriages that are alternately in engagement with the pipe blank frequently leads to critical, non-uniform advancing movements, and this can have a disadvantageous effect on the quality of the finished rolled pipe. In this connection, a rolling process in copper rolling should be specifically mentioned, which is very sensitive in this regard and is therefore particularly susceptible to failure, in contrast to others.
In this regard, relatively great regulation effort with regard to the individual advancing carriages is required, in order to be able to undertake a hand-over from one advancing carriage to the other without sudden movements and without any negative influence on the rolling process.
However, this furthermore also leads to increased maintenance effort for such a pipe blank advancing apparatus, because changes or adaptations, for example with regard to friction behavior of “advancing carriage/pipe blank” make more frequent adjustments of the advancing carriages necessary.